Apparatus for closing and sealing bag tops



Sept. 1, 1964 F. L. HOPKINS APPARATUS FOR CLOSING AND SEALING BAG TOPS Filed June 8. 1961 3 Sheets-Sheet 1 IN V EN TOR. FRANK L HOPK/NJ ATTORNEY:

Sept. 1, 1964 F. 1.. HOPKINS APPARATUS FOR CLOSING AND SEALING BAG TOPS Filed June 8. 1961 3 Sheets-Sheet 2 M350 m2. WQQ

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3 Sheets-Sheet 3 F. L. HOPKINS FOR CLOSING AND SEALING BAG TOPS APPARATUS Sept. 1, 1964 Filed June 8, 1961 v" v I INVENTOR. FRA NK L HoPK/Ms BY I 71/ *LJ AT'r-aRNEYJ United States Patent 3,146,564 APPARATUS FOR CLOSING AND SEALING BAG TOPS Frank L. Hopkins, Minneapolis, Minn., assignor to Bemis Bro. Bag Company, Minneapolis, Minn, a corporation of Missouri Filed June 8, 1961, Ser. No. 115,724 2 Claims. (Cl. 53-139) This invention relates to new and useful improvements in machines for closing and sealing the open tops of relatively large flexible walled bags by firmly pressing the bag top walls into flatwise relation and securing them together in leakproof relation to provide a strong durable closure capable of withstanding rough handling, when moved about from place to place.

An object of the present invention is to provide a machine of the general character disclosed in Patent No. 2,845,760, granted August 5, 1958, wherein induction heating is utilized in the operation of sealing the bag tops.

At the present time it is common practice, after the bag bodies have been filled, to press the bag top walls into flatwise relation and securing them together by stitching or by an adhesive, or by both, and applying a strip of pressure sensitive sealing tape over the flattened bag top walls and firmly pressing the tape into bonding engagement with the bag top walls and around the stitching by suitable means such as a pair of opposed pressure rollers or elements, thereby to assure the formation of a leakproof closure.

Some sealing tapes now utilized for sealing bag tops have an adhesive embodied therein which may be reactivated by the application thereto of direct heating and pressure, thereby to seal the tape to the bag top walls. There are many disadvantages to direct heating. For example, a large heating surface is required to reactivate the adhesive. It also requires a relatively high temperature to assure adequate penetration of the adhesive into the paper plies of a multiwall bag top, particularly when an inner adhesive coated moistureproof foil liner is used, which may cause scorching of the tape and bag top walls, and weakening of the paper fibres. Furthermore, the heat cannot be applied uniformly throughout the tape and bag top walls, and it may therefore be necessary to preheat or warm the bag tops before starting the bag seal-ing operation.

An important feature of the present invention is directed to the sealing of bag tops by transfer of heat to the metallic foil of the tape which activates the bonding agent by induction heating. Some moistureproof multiple wall bags now in common use have an inner metallic foil liner which extends the full height of and constitutes a portion of the bag top walls, when said walls are pressed into flatwise relation and secured together. The tape used for sealing the flattened bag top walls may also be made of paper comprising a metallic inner foil liner having a bonding agent incorporated or embodied therein to be reactivated by pressure or heat or both. By utilizing induction heating to heat the metallic foil to reactivate the adhesive coating on the inner foil liner and on the tape, such reactivation of the adhesives may be quickly accomplished without any possible danger of breaking down or weakening the walls of the bag top, which may occur when applying direct heating to the tape and bag top walls, because such a high temperature would be required to penetrate the paper plies.

Another object of the invention is to provide a unique method of and apparatus for hermetically sealing flattened bag tops that is highly efficient and practical; provides instantaneous controlled heat; insures a strong tight bond; assures uniform distribution of the heat throughout 3,146,564 Patented Sept. 1, 1964 "ice the area to be heated; and wherein there is no direct contactbetween the heating elements and the surface to be heated.

These and other objects of the invention and the means for their attainment will be more apparent from the following description taken in connection with the accompanying drawings.

In the accompanying drawings there has been disclosed a structure designed to carry out the various objects of the invention, but it is to be understood that the invention is not confined to the exact features shown, as various changes may be made within the scope of the claims which follow.

In the drawings:

FIGURE 1 is a side elevational View of a portion of a bag top closing and sealing machine of the general type disclosed in Patent No. 2,845,760, with some of the parts omitted and showing the invention embodied therein;

FIGURE 2 is a plan view of FIGURE 1 showing the travel path of the bag tops and the various stations through which the bag tops pass in the operation of closing and sealing their open tops;

FIGURE 3 is an enlarged detail view partially in section showing the induction heating device, station F;

FIGURE 4 is a transverse sectional elevation on the line 44 of FIGURES 1 and 2;

FIGURE 5 is a detail sectional elevation on the line 55 of FIGURE 4; and

FIGURE 6 is an enlarged detail sectional view of a sealed bag top showing the upper marginal wall portions of the inner metallic foil liner and the bag top walls and tape intimately bonded together to provide a leakproof closure.

In the selected embodiment of the invention as herein disclosed there is illustrated in FIGURES 1 and 2, a portion of a bag top closure and sealing machine comprising a plurality of stations through which the bag tops are successively passed in the operation of closing and sealing the bag top walls. The machine shown in FIGURES 1 and 2, with the exception of station F, is well known in the art and it is therefore believed unnecessary to further illustrate the same in detail.

The machine, as best shown in FIGURE 2, comprises base plates 6 and 7 spaced apart to provide a passageway therebetween for the flattened bag tops. A bag top receiving and guide member 8 of inverted U-shape cross-section, is shown having its opposed side walls outwardly flared, as indicated at 9, station A. The bag tops are directed into the guide member 8 by the operator, as the bags are conveyed through the machine by a suitable conveyor, not shown in the drawings. From guide member 8, station A, the flattened bag top passes through station B which comprises a sewing head for sewing the flattened bag top walls together across the width of the bag top. From station B, the sewn bag top passes through a thread clipper, station C, which cuts the chain thread between adjacent bag tops as will be understood.

From station C, the sewn bag top 12 passes through a tape folder (station D) which folds a strip of sealing tape 13 over the sewn bag top walls, as best illustrated in FIG- URE 6. The bag top with the tape applied thereto then passes between a pair of opposed pressure elements or rollers 1414 which squeezes the tape firmly into engagement with the outer plies of the flattened bag top. It is to be understood that the inner surfaces of the sealing tape are of a metallic foil coated with a bonding agent such as thermoplastic which may be reactivated by the application of heat and pressure thereto.

The tape-covered bag top next passes through the tape clipper, station E, which clips the sealing tape between adjacent bag tops as the bag tops advance through the machine. From the tape clipper, station E, the flattened bag tops pass through a heating device which serves to reactivate the adhesive coatings on the walls of the metallic foil liner and the sealing tape. This heating device constitutes an important feature of the present invention.

The present invention is directed more particularly to an improved method of an apparatus for closing and sealing the open tops of large multiwall bag bodies each comprising a plurality of paper plies, generally indicated by the numerals l6 and 17, and an inner metallic moistureproof foil liner 18. The upper end of the inner foil liner 18 extends substantially to the top end of the bag body, as clearly indicated in FIGURE 6. In this figure a strip of sealing tape 13 is shown folded over the bag top walls with its opposed sides overlying and concealing the chain stitching. It has been discovered that when an inner metallic foil lineris embodied in the bag top, the metallic foil liner may readily and quickly be heated to reactivate the adhesive coating or bonding agent thereon by the use of induction heating, thus eliminating the ever present hazard of scorching and weakening the bag top walls by the application of high temperature, as when using direct heat.

The induction heater, as best illustrated in FIGURES 3, 4 and (station F), is of well known construction, and it is therefore believed unnecessary to herein describe the same in detail. It comprises a tubular coil, generally designated by the numeral 19, preferably oval in configuration, as indicated in FIGURE 5, and disposed in parallel relation to the travel path of the bag tops, as best shown in FIGURE 3. Coil 19 is provided with offset spaced terminals 21 and 22 shown secured in a pair of conductors 23 and 24, respectively, having their opposite ends electrically connected to a pair of mounting brackets 25 and 26, respectively, secured to a housing 27 by suitable means such as bolts or screws 28. Conductors 23 and 24 and their respective mounting brackets 25 and 25 are insulated from one another by a suitable insulator 29 interposed between conductors 23 and 24 and extending rearwardly between brackets 25 and 26, to also insulate these parts from one another, as will be understood.

Conductors 23 and 24 and their respective brackets 25 and 26 are shown provided with fluid circulating channels 30 which are in direct communication with the fluid passage 31 in heating coil 19. The opposite ends of channels 39 are connected to a suitable source of fluid supply under pressure, not shown, provided in the lions ing 27 whereby a suitable coolant may be circulated through the heating coil during operation of the heater, thereby to maintain the outer surface of the coil Suficiently cool to prevent it from scorching the walls of the tape or bag top, as each bag top passes through station F. The coolant circulating means and current supply means for the induction coil U are contained within housing 27, and are of well known construction and therefore need not be described in detail.

To hold the bag tops in engagement with the heating coil 19, a spring pressed ceramic pressure element 32 is mounted for pivotal movement about a vertical axis, as illustrated in the drawings. Pressure element 32 has a hub 33 apertured to receive a pivot stud 34 having its lower end suitably secured to the base plate 7 of the machine frame, as shown in FIGURE 4. A spring 35 is shown having one end secured to the hub 33 of the pressure element 32 by a stud 36. The opposite end of spring 35 may be anchored to base plate 7, as indicated at 3?.

In the operation of closing and sealing the open tops of large multiwall bags, the bags are placed upon a conveyor, not shown, and the open top of each bag is then directed into the guide member 8, station A, at the receiving end of the machine which initially presses the bag top walls into fiatwise relation. From station A, the flattened bag tops are successively delivered to the sewing head, station B, which secures the flattened bag top walls together by a row of stitches extending the length of the bag top.

The stitched bag tops then advance through the thread clipper, station C, whereby the section of chain stitching between adjacent bag tops is severed to free the bags from one another. However, before the section of chain stitching between adjacent bag tops is severed, the leading end portion of the bag top of the leading bag has entered the tape folder, station D, where a strip of thermoplastic coated sealing tape is folded over the sewn bag top with the opposed sides of the tape overlying and concealing the chain stitching in the bag tops. As each tape-covered bag top leaves the tape folder, station D, it passes between a pair of squeezing elements on rolls 14, which firmly press the tape into engagement with the bag top walls.

As each bag top passes from station D, it passes through a tape clipper, station E, and into the field of high frequency current generated between the heating coil 19 and the inner metallic foil liner 18 in the bag top. Such transmission of induced current between coil 19 and the liner 18 instantly heats the metallic foil liner 18 and thereby reactivates the thermoplastic coating thereon, whereby the bag top Walls, including the inner metallic foil liner and tape may be intimately welded and bonded together to provide a leakproof closure. To assure a leakproof seal, the neated bag tops are fed between a series of compression rolls 37-37 and 3838, station G, and as the trailing end of each bag top approaches station F, the tape cutter at station E is automatically actuated to clip the tape between adjacent bag tops, and thus separate the scaled bags from one another.

The present invention has been found extremely practical and eflicient in actual use. By utilizing induction heating for reactivating the thermoplastic coating or bonding agent on the metallic foil liner of bag top walls, the reactivation period may be greatly expedited, resulting in greater economy; it provides fast controlled heat; does not scorch outside of tape or bag walls during the heating process; makes it possible to use smaller heating elements, resulting in greater compactness; no warm-up period is required; uniform distribution of heat throughout tape and bag top Walls; no direct contact is required between the heating coil and the surface to be heated; and it presents the utmost in simplicity and construction.

The present invention is particularly applicable for closing and sealing multiwall bag bodies having an inner foil liner embodied in the walls of the bag body which extends to the top of the bag top walls, although it may be used with other types of bag bodies, and with or without a sealing tape.

It is apparent that many modifications and variations of the invention as hereinbefore set forth may be made without departing from the spirit and scope thereof. The specific embodiments described are given by way of example only and the invention is limited only by the terms of the appended claims.

I claim as my invention:

1. In a machine for closing and sealing the open tops of filled flexible walled paper bags, the walls of each bag comprising a plurality of paper plies and an inner metallic foil liner, and the inner surfaces of said liner having a thermoplastic coating applied thereto, means for pressing the open bag top walls including the liner into flatwise relation and securing them together to close the bag tops, means for folding a strip of foil lined thermoplastic coated sealing tape over each flattened bag top, an induction coil located adjacent to the travel path of the bag top and connected to a source of electrical energy, means cooperating with said coil to produce a field of high frequency current for the transfer of electrical energy between said coil and the metallic liner in the bag top and tape, thereby to induce heat in the foil liners through the insulating barrier of the paper bag walls and sealing tape to quickly and controllably heat the foil liners which in turn reactivate the thermoplastic coatings on the liner and tape without deleteriously heating the paper bag Walls and sealing tape, and means for firmly pressing the heated bag top walls and tape into intimate bonding engagement to seal the bag top.

2. In a machine for closing and sealing the open tops of filled flexible walled paper bags, the walls of each bag comprising a plurality of paper plies and an inner metallic foil liner, and the inner surfaces of said liner having a thermoplastic coating applied thereto, means for pressing the open bag top walls including the liner into fiatwise relation and securing them together by a row of stitches, means for folding a strip of foil lined thermoplastic coated sealing tape over the sewn bag top walls, means for initially pressing the opposed sides of the sealing tape into bonding engagement with the walls of the bag top, an induction coil located adjacent to the travel path of the tops and connection to a source of plastic coatings on the liner and tape without deleteriously heating the paper bag Walls and sealing tape, and means for firmly pressing the heated bag top walls and tape into intimate bonding engagement to seal the bag top.

References Cited in the file of this patent UNITED STATES PATENTS 2,697,533 Richard Dec. 21, 1954 2,727,648 Grevich Dec. 20, 1955 2,845,760 Hopkins et al. Aug. 5, 1958 2,937,481 Palmer May 24, 1960 2,946,168 Manwaring et al. July 26, 1960 

1. IN A MACHINE FOR CLOSING AND SEALING THE OPEN TOPS OF FILLED FLEXIBLE WALLED PAPER BAGS, THE WALLS OF EACH BAG COMPRISING A PLURALITY OF PAPER PLIES AND AN INNER METALLIC FOIL LINER, AND THE INNER SURFACES OF SAID LINER HAVING A THERMOPLASTIC COATING APPLIED THERETO, MEANS FOR PRESSING THE OPEN BAG TOP WALLS INCLUDING THE LINER INTO FLATWISE RELATION AND SECURING THEM TOGETHER TO CLOSE THE BAG TOPS, MEANS FOR FOLDING A STRIP OF FOIL LINED THERMOPLASTIC COATED SEALING TAPE OVER EACH FLATTENED BAG TOP, AN INDUCTION COIL LOCATED ADJACENT TO THE TRAVEL PATH OF THE BAG TOP AND CONNECTED TO A SOURCE OF ELECTRICAL ENERGY, MEANS COOPERATING WITH SAID COIL TO PRODUCE A FIELD OF HIGH FREQUENCY CURRENT FOR THE TRANSFER OF ELECTRICAL ENERGY BETWEEN SAID COIL AND THE METALLIC LINER IN THE BAG TOP AND TAPE, THEREBY TO INDUCE HEAT IN THE FOIL LINERS THROUGH THE INSULATING BARRIER OF THE PAPER BAG WALLS AND SEALING TAPE TO QUICKLY AND CONTROLLABLY HEAT THE FOIL LINERS WHICH IN TURN REACTIVATE THE THERMOPLASTIC COATINGS ON THE LINER AND TAPE WITHOUT DELETERIOUSLY HEATING THE PAPER BAG WALLS AND SEALING TAPE, AND MEANS FOR FIRMLY PRESSING THE HEATED BAG TOP WALLS AND TAPE INTO INTIMATE BONDING ENGAGEMENT TO SEAL THE BAG TOP. 